The PSI5 bus (see “PSI5 V2.1, Technical Specification, Peripheral Sensor Interface for Automotive Applications, 8 Oct. 2012”) is a two-wire bus which ensures the voltage supply of slave participants and the communication on the same line pair.
In the idle mode, a master participant supplies the bus with a supply voltage, typically in the range between 4.4 V and 11 V. The master communicates with the slaves via sync pulses which are short voltage pulses on the line pair. A slave communicates with the master via a current interface: For transmission, the slave temporarily applies a current which is detected by the master with the aid of an installed current sink. Due to a relatively high signal current of 26 mA and the bit coding in the Manchester Code, a high interference protection is achieved, whereby the use of a cost-effective, twisted two-wire line is sufficient for wiring. The data words include two start bits each, 8 to 24 data bits, and a parity bit or 3-bit CRC (cyclic redundancy check).
The PSI5 bus is used in motor vehicles for the communication between a control device (master) and one or multiple sensors (slaves). Point-to-point and bus configurations including asynchronous and synchronous communication are supported. In previous applications, the bus is either completely active or completely deactivated by turning off the voltage.
For some new applications, it may be meaningful, however, to transfer the bus into a standby state in which communication does not take place, but individual or all slaves are still active at a reduced power consumption and may restart the bus communication if a certain event occurs.
A master/slave communication system is also provided in German Published Patent Application No. 102012205160. Here, individual participants may be transferred into a standby mode or into a sleep mode with the aid of a message.